Pfizer Handbook of Microbial Metabolites 662 



streptomycin. Its effect on Escherichia coli has been 

 studied.^ The cell permeability barrier was altered, remi- 

 niscent of detergents and of polymyxin. Preformed cells 

 were undamaged, but defects were caused in cell mem- 

 branes formed in its presence by non-resistant cells. 

 When C^Mabeled streptomycin was used, initial uptake 

 occurred only outside the cell wall and secondary uptake 

 depended on secondary damage to the membrane. The 

 growing membrane was the primary site of action of the 

 antibiotic. 



The effect of streptomycin on the excretion of nucleo- 

 tides by E. coli has been investigated.'* Streptomycin en- 

 hanced excretion of 5'-nucleotides and prevented excre- 

 tion of 2'- or 3'-nucleotides. It was not clear whether 

 streptomycin blocked RNA synthesis de novo or whether 

 degradation of RNA to 5'-nucleotides was enhanced. 



The same group has published on chloramphenicol-sen- 

 sitive and chloramphenicol-insensitive phases of the lethal 

 action of streptomycin.'^ It appeared that the lethal ef- 

 fect of streptomycin on E. coli was exerted in two phases 

 (1) a preparatory phase, which is markedly less lethal 

 and can be blocked by chloramphenicol (a protein syn- 

 thesis inhibitor), followed by (2) a more direct lethal 

 phase which is insensitive to chloramphenicol. The in- 

 duction process might have been due to formation of a 

 permease without which streptomycin could not accumu- 

 late in the cell in lethal concentration. 



It has been found that, while penicillin inhibits growth 

 of Staphylococcus aureus (strain Duncan), it does not 

 cause rapid lysis as, e.g., in the case of E. coli. Penicillin 

 and streptomycin added (each at minimally bactericidal 

 concentrations) to exponentially growing cultures caused 

 rapid lysis. Only antibiotically active forms of strepto- 

 mycin were effective. Under anaerobic conditions lysis 

 was not rapid. (Streptomycin is not ordinarily effective 

 under such conditions.*^) 



•^Nitya Anand and Bernard D. Davis, Nature 185 22, 23 (1959). 

 * Carmen L. Rosano, Richard A. Peabody and Charles Hurwitz, 

 Biochim. et Biophys. Acta 37 380 (1960). 



5 Charles Hurwitz and Carmen L. Rosano, ibid. 41 162 (1960). 

 6R. Hancock, Nature 186 658 (1960). 



